In Creepy Steeple, after you've freed the Boos, stand still in the main room.Wait for some Boos to start sticking to you, the use your Super Hammer attack to shake them off. Do this twice, and the Boos will get mad and form the Atomic Boo. When beaten, he will drop the Lucky Start badge. This is needed if you want to fill up your Tattle Log and get all badges.